1. Field of the Invention
The present invention relates to a wireless access system for performing client cooperation transmission, and more particularly, to a method and apparatus for performing client cooperation transmission through a group resource allocation (GRA) scheme.
2. Related Art
A group resource allocation (GRA) scheme is a method of allocating resources to several users (i.e., terminals) belonging to one group to decrease an overhead of a control message transmitted by a base station (BS) to the terminal.
By using the GRA scheme, the BS can transmit control information, which is reported to the terminals when allocating the resources individually to the terminals, by compressing the control information in a group unit. Therefore, a signaling overhead can be decreased in a network.
The BS can use group control information to allocate and configure resources to one or more terminals belonging to one group. In this case, the group control information can be called an advanced MAP or an A-MAP. Regarding user-specific control information for a single user or a user group, multiple information elements are coded individually for the A-MAP. In addition, the A-MAP is transmitted by being cyclic redundancy check (CRC)-masked with a terminal identifier (ID) (e.g., an STID of a specific terminal, a broadcast STID, and/or a multicast STID).
Since the A-MAP is transmitted by being individually encoded and masked with the STID, the terminal performs blind decoding on an area in which the A-MAP is transmitted in order to confirm a presence/absence of an A-MAP transmitted to the terminal itself. In this case, the terminal can detect the A-MAP by using the STID assigned to the terminal itself, the broadcast STID, and/or the multicast STID (e.g., a group ID, a persistent ID, a sleep/idle mode ID, an MBS ID, etc.).
The terminal performs blind decoding on the basis of a MAP size used in a corresponding system. In this case, the BS and/or the terminal can limit the MAP size or type to a specific size and a specific type in order to decrease the number of blind decoding attempts. For example, the BS and/or the terminal can limit a size of an A-MAP information element (IE) to either three types of sizes, i.e., 56 (or 64), 96, and 144 bits or to two types of sizes, i.e., 56 (or 64) and 96 bits.
A case is assumed in which one minimum A-MAP logical resource unit (MLRU) consists of 48 data sub-carriers, two MLRUs consist of 96 data sub-carriers, and a size of the A-MAP IE is determined to 56 or 96. In this case, by using an encoding scheme (e.g., tail-biting convolutional coding (TBCC) or puncturing) for a downlink control channel, the BS can transmit A-MAP IEs by mapping a 56-bit A-MAP IE to one MLRU and by mapping a 96-bit A-MAP IE to two MLRUs.